Mar. 17,1923 Influence of Soil Temperature on Seedling-Blight 
843 
content by sprinkling the plot the day before planting. Soil-moisture 
determinations were run before each seeding to insure similar moisture 
conditions. Thus temperature was the chief soil variant for each seeding, 
at least during the seedling stage. Of course light intensity and the 
duration of the light varied for the different seedings, and such factors 
must be taken into consideration in all work of this type. 
INOCULATION TECHNIC 
In both wheat and corn the inoculations were made by using a water 
suspension of conidia of Gibberella saubinetii. The conidia were obtained 
from 3-to-4~day-old cultures. Comparative inoculations with these vege¬ 
tative conidia and the conidia produced at the end of the vegetative 
period gave the same type and percentage of blighting. Therefore the 
vegetative conidia were used, as they could be produced* much more 
rapidly and uniformly. 
Sufficient seed for each can of the series was soaked for 10 minutes in 
the water suspension of the co¬ 
nidia, after which each kernel 
was lifted out separately with 
sterile forceps and placed in the 
sterilized soil in the can. The 
controls were similarly treated in 
sterile distilled water. 
In several of the early inocula¬ 
tion experiments the number of 
conidia in the suspension seemed 
to have a marked influence not 
only on the percentage of blight 
produced but also upon the type 
of blight that resulted. At the 
outset, therefore, it was necessary 
to take up a study of this phase 
of the problem and determine the 
influence of the number of conidia 
introduced with the seed on the 
percentage of blight occurring 
and the type of blight developing, as well as to determine what spore con¬ 
centration was most capable of producing a consistent and uniform type 
of blighting. 
The regular temperature cans were prepared, as previously described 
under the discussion of methods, and filled with soil at 60 per cent of the 
moisture-holding capacity. The cans were placed in the greenhouse at a 
temperature of 16 0 to 20° C. Uniformly plump seed of both Marquis 
and Turkey wheat was soaked in conidial suspensions ranging from about 
13,200 conidia per cubic centimeter to 1,625,000 conidia per cubic centi¬ 
meter in the most concentrated spore suspension used. These suspen¬ 
sions were prepared by making up a large quantity of a heavy suspension 
of conidia obtained from vigorous young cultures. The average of a large 
number of conidial counts made on the haemocytometer was taken as the 
basis for making the spore dilutions. 
With the increase in the number of conidia, there resulted a marked 
increase in the percentage of diseased plants. Further, with the increase 
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Fig. 3. —Graph showing relation of number of conidia 
in the inoculum to the development of seedling* 
blight of wheat. The increased rate of application 
of conidia in the inoculum on the seed gradually 
increased both the severity of the blighting and the 
percentage of plants blighted before emerging. 
